Cancer of the mammary glands is the third most common type of cat cancer, the first two being lymphoma in cats and skin cancer. Most of the time, mammary cancer is malignant, and almost all cases originate from the glandular epithelium. Even male cats can develop mammary carcinoma, and the clinical course that needs to be followed is similar to the one recommended for female cats.
The size of the mammary tumor determines prognosis and survival times. Cats with a tumor less than three cm in size may live up to 21 months after diagnosis, and those with bigger tumors have an average survival time of a year.
A single or multiple palpable mass under the skin of the abdomen is the most common indicator of the presence of a tumor. Other signs include weight loss, appetite loss, general weakness and swelling in one or both legs.
Benign and malignant tumors are almost similar in shape, except that the former are well-circumscribed and firm, while the latter are aggressive and metastasize fairly fast. Other defining factors of mammary tumors are that they have undefined borders and are fixed to the skin or underlying tissue.
There are very few treatment options, and surgery is the preferred choice for all mammary tumors – benign as well as malignant. The type of surgery depends largely on the size, location and number of tumors. Before exercising the surgical option, it is necessary to determine if the tumor is inflammatory mammary carcinoma, because these are generally not able to excise.
There is a major difference between mammary cancer in dogs and cats. In cats, mammary cancer is much more aggressive and prognosis is much more guarded. Consulting a veterinary oncologist is necessary because feline breast cancer is associated with a greater risk of metastasis. In dogs, surgery is generally conservative, involving the removal of either the mass or the gland affected by cancer. On the contrary, one or both mammary chains have to be removed in cats.
Mammary tumors can be prevented by spaying cats at an early age. Spaying after two years of age is not as effective. It is most effective if the cat is spayed before it reaches its first heat, which is approximately 6 months of age.